1. Field of the Invention
This invention relates generally to the determination of various parameters in a subsurface formation penetrated by a wellbore while drilling the wellbore. More particularly, this invention relates to the determination of formation parameters such as formation pressure through the use of a non-rotating drill string stabilizer.
2. Description of the Related Art
Present day oil well operation and production involves continuous monitoring of various subsurface formation parameters. One aspect of standard formation evaluation is concerned with the parameters of reservoir pressure and the permeability of the reservoir rock formation. Continuous monitoring of parameters such as reservoir pressure and permeability indicate the formation pressure change over a period of time, and is essential to predict the production capacity and lifetime of a subsurface formation. Present day operations typically obtain these parameters either through wireline logging via a "formation tester" tool. This type of measurement requires a supplemental "trip", in other words, removing the drill string from the wellbore, running a formation tester into the wellbore to acquire the formation data and, after retrieving the formation tester, running the drill string back into the wellbore for further drilling. Thus, it is typical for formation parameters, including pressure, to be monitored with wireline formation testing tools, such as those tools described in U.S. Pat. Nos.: 3,934,468; 4,860,581; 4,893,505; 4,936,139; and 5,622,223.
Each of the aforementioned patents is therefore limited in that the formation testing tools described therein are only capable of acquiring formation data as long as the wireline tools are disposed in the wellbore and in physical contact with the formation zone of interest. Since "tripping the well" to use such formation testers consumes significant amounts of expensive rig time, it is typically done under circumstances where the formation data is absolutely needed or it is done when tripping of the drill string is done for a drill bit change or for other reasons.
The availability of reservoir formation data on a "real time" basis during well drilling activities is a valuable asset. Real time formation pressure obtained while drilling will allow a drilling engineer or driller to make decisions concerning changes in drilling mud weight and composition as well as penetration parameters at a much earlier time to thus promote the safety aspects of drilling. The availability of real time reservoir formation data is also desirable to enable precision control of drill bit weight in relation to formation pressure changes and changes in permeability so that the drilling operation can be carried out at its maximum efficiency.
It is desirable therefore to provide a method and apparatus for well drilling that enable the acquisition of various formation data from a subsurface zone of interest while the drill string with its drill collars, drill bit and other drilling components are present within the well bore, thus eliminating or minimizing the need for tripping the well drilling equipment for the sole purpose of running formation testers into the wellbore for identification of these formation parameters.
To address these shortcomings, it is a principal object of the present invention to utilize at least one of the drill string components for obtaining such formation parameter data.
More particularly, it is an object of the present invention to utilize a non-rotating stabilizer tool on the drill string for engaging the formation to gather information therefrom.